Ah, Biden is pretty much doing exactly what Trump started. Most of what you hear to the contrary is just political rhetoric.
Well, we have to look at this in as exact an order as we can. The US was hesitant to get involved in either of the world wars. After WWII, we were staring across the field at a huge soviet army. Everything you mention in your post were tools we used to protect ourselves from that army. That army is gone, and nukes aside. Russia appears to be a paper tiger. So, we don't need those tools anymore. Like you say, we have tremendous infrastructure concerns that have to