I think this thread belongs in the Political forum.
Some comments:
Manufacturing in China depends on the market outside of China, much of it in the USA, if the economy in the USA goes down then so will the market and the demand and the manufacturing.
Manufacturing in China is good for many other countries, not only because it provides large numbers of inexpensive products but because China has also become a large consumer of copper, steel, machinery, etc., whatever they need for their manufacturing.
It's OK to decide how many immigrants a country will accept and what profile immigrants should have, for example if there is a shortage of farmers or computer programmers or whatever. The problem is that it cannot be enforced, sealing the borders immediately just cannot be done.
If people from third world countries cannot go to the USA and get jobs, then the jobs will likely go out of the USA to third world countries.
Illegal immigrants in the USA are important for USA economy, in the past there have been attempts to legalize them by giving resident status to all illegals that have been in the USA for a certain time, but this has not solved the problem because more illegals keep getting in all the time, many of the illegals do not want to stay in the USA, they just want to go for a while, make some good money and then go back to their countries and families (this is at least what I see as a Mexican but I would guess it's the same for others)
IMHO the USA is very capable of competing with Chinese manufacturing particularly in high end good quality products, I'm outside the USA and keep buying USA products even though I pay for them a lot more than what USA citizens do.
It's true that most of electronic manufacturing has moved out of the USA, but that has not made the USA a weak economy and has not made electronics any less available to the American consumer.
The USA is a nation of immigrants, immigrants have made it strong and free, I think immigration has been good in the past and is good now.
Perhaps a bit off topic but since you brought up the immigrants issue hey, from a Mexican point of view I could say that it was US immigrants who declared and made Texas independent from Mexico, that wasn't so bad for Texas was it?, I guess if I had been there at the time I would have probably taken their side (don't worry I don't think that Mexican immigrants in California are interested in declaring California's independence any time soon).
The USA will continue to be very strong for a very long time.
Luis