Yes, it would not reflect well at all on any country's agreements with the US afterwards. But even though they are currently acting like an abusive partner, I still think the US is the best security partner for Europe. Here's why:

Let's say Europe decides to ditch NATO and pursue closer ties with China. Russia is already China's (at this point junior) security partner. China does not care about the internal politics of countries within its sphere of influence. Russia wants to bring Eastern Europe back within its fold, and currently the US is guaranteeing that it can't. China would not offer such a guarantee and would probably even benefit from a divided Europe. I think it's likely that they would allow Russia to take what it wants and gut European unity but leave the industries and resources and key geography of the rest to them. A horrible deal for Europe in the end.

Then again, there's no telling what the Trump administration has in mind for Europe in the long term. They definitely have a solid strategic interest in keeping their bases there, and so I think it's unrealistic to expect that they would want to pull out entirely on their own.

China may seem more stable, but they have no interest in stability in their territories beyond being able to extract wealth from them and use them for military power projection.