Armed citizens wouldn't stop such an invasion if they are continually fucked over by their own police/politicians while the invaders get paid to sit around and make babies (and vote Commie) instead of having to work, for a fraction of that money, if they stayed in their own country.
If armed citizens tried to stop a caravan if it was in the US, or if they tried to 'encourage' them to leave one by one after they were already spread out, such resistance would be shut down PDQ even under Trump.