Such asymmetric strategies are being employed by our competitors, like China, Iran, and Russia. All three have a very robust anti-access/area denial capability which can disrupt NATO/multilateral operations in event of war. Most notably, China's huge reserve of ballistic/cruise missiles, submarines, and mines enable it to effectively carve out an inaccessible area of ocean up to the first island chain. Despite our ability to best China's fleet in a conventional, World War Two-style naval engagement, they have created a strategy that can target our weaknesses: everything from gaps in our missile defense to our cyber infrastructure.
However, Iran and Russia are not to be ignored. NATO's ability to respond to rapid territorial aggression in Eastern Europe by Moscow would be severely hampered by a flurry of ballistic missiles launched at incoming supply lines. Though it has been over a decade since Operation Mellinium Challenge 2002, both Iran's ability to close down the Strait of Hormuz--if only temporarily--and America's vulnerabilities in littoral areas remain apparent, even as we continue forward with programs designed to help us "win" in such environments.
But perhaps more broadly, we've seen less capable nations match or exceed our own geopolitical influence on a regional level. In rather Cold War-esque fashion, some of the biggest strategic victories are being won under the veil of political subversion, covert operations, and back door economic support. Arguably, NATO remains far more vulnerable to a Ukraine-style invasion of a member state than a conventional invasion envisioned by the strategists of Cold War-era battle plans. The Baltic states all possess significant ethnic Russian populations, with a large portion feeling closer to Moscow than their respective governments. Should Russia arm internal dissidents in Baltic, how would NATO respond? Potentially with a prolonged insurgency against ethnic insurgents, which would enable Russia to wage war against the alliance via prolong. However, would they retaliate against Russia, risking a conventional conflict and its associated economic impacts? It's a question that I cannot begin to answer, but I will say that America did not attack the Soviet Union over its support of North Vietnam (which included shooting down U.S. aircraft). But at the same time, South Vietnam was not a NATO member.
Iran has created a regional network of non-state and state alliances, which has enabled it exert a large degree of influence in the Middle East. Hezbollah, one of the major non-state actors engaging in conflict within Syria, is funded and guided by Iran. With the help of tactical advice, training, and weapons shipments from Iran (coupled with war's version of natural selection), Syria's third-rate army has evolved into a resilient and effective force that has achieved several strategic victories against opposition forces. On a more economic level, Iran's tanker fleet has circumvented oil embargoes on Syria, which has kept the regime's war machine rolling on. In terms of political subversion, Iran was responsible for backing the 2007 coup that supplanted the Palestinian Authority with Hamas in the Gaza Strip, a major setback for Israeli security and American political interest in the territories. In Iraq, Iran has reportedly deployed 500 members of the Iranian Revolutionary Guard Corps to the country and dispatched the Quds Force's leading general to coordinate the defense of Baghdad.
Conventional power is important, but it does not always translate into strategic success. Asymmetrical opponents have devised dangerous ways to defeat our military forces. But perhaps more imminent, regional powers have been expanding their influence in ways America cannot match without risking the very likely possibility that our efforts will backfire. As these situations continue to develop, citizens and policymakers alike will have to remember that threats don't always come in the form of armies and terrorists--it's the ghosts fomenting unrest in the corner that can pose the true threat.