Assistant professor position in USA (9 months). Is it badly seen to spend the summer to work at distance in my home country? I will start soon an Assistant professor position in USA in Engineering. During the first 2 years the summer is paid. From the third I hope to get funded with grants. Is it badly seen if I spend the summer to work at distance in my home country? 

EDIT: I will have 2 PhD students in the start-up, mine will be a computing lab so 99% percent of things and supervising can be done remotely.
A lot of this will depend on your department's culture regarding 9-month appointments. There are at least two different aspects of this I can think of:


How are 9-month appointments actually viewed? In some places I've been, 9-month positions, especially if the pay is spread over 12 months, are functionally just "75% Hard Money" positions, and there's a pretty clear expectation that you're working in the summer, etc. rather than "an unfunded summer is a summer off". If the summer ends up having a lot of committee meetings, etc. that could be a problem.
How are long absences viewed? There are some departments, especially those with lots of field work, being gone all summer would be quite typical. There are others where it would be extremely conspicuous, and probably be the source of some concerns about collegiality come evaluation time.