closing borders, specially in a country as big and with as many entries as the US, has a marginal effect. The UK had some models (previous to this pandemic) that pointed out that a 99% border closure (which seriously affects commerce and supply chains) only delays the peak of the outbreak by few weeks at most.
The idea is that it's enough with one infected to go through the borders without detection, and at that point, with this disease, the outbreak is already on. If you closed too much, you just fucked yourself and still end up with an outbreak. Instead, focus on testing capabilities to detect the inevitable outbreaks and control them with quarantines and social distancing.
Russia is as trustworthy as China is with their numbers. Even then, the number of cases right now doesn't matter as much as the rate of growth, which right now is doubling every 5 days, worse than the US is doing now. So yeah, they closed the borders but now they need to take social distancing measures as everyone else.
Also, per capita infections is a worthless measure. The spread is not limited by population, what matters is the number of outbreaks. Two large outbreaks in the US are worse than one smaller outbreak in a smaller country, despite the second having a higher per-capita rate
