These things are partially connected. For example, in 2015 Merkel famously invited all asylum seekers to Germany. Now they reintroduced border checks… on the Polish border but back then they refused to even acknowledge the fact that the migration crisis was engineered by Belarus and Russia, even when Lukashenko said that explicitly. This denial not only convinced them of their impunity, but also aggravated the problems they caused, and gave rise to the far-right. When people see that the ruling party can’t deal with a problem, they will resort to one that does - or at least claims so.
Can’t say much about US, but I suppose it’s the same there.