Experiences like these can negatively colour a visitor's impression of the country and its people.
The question of catcalling/street harassment is highly relevant for exchange participants. Getting unwanted attention is never a pleasant experience, particularly when you're many miles from home and perhaps a bit vulnerable. My first experiences with street harassment were during my university years, and I remember several instances that took place during my first months in the UK. I didn't always understand what guys were saying, either, thanks to a combination of slang and accents (in Glasgow, I just smiled and carried on walking, no clue what he'd said...). If I had these kinds of difficulties, as a native speaker of the local language, I can only imagine how difficult it must be for people facing a language barrier.
An American friend studying architecture in Rome was lost and asked a man for directions, and he replied "I can tell you how to get to my place." When she found a police officer, she got the directions she needed but received no sympathy about the first creep--"Well, can you blame him? You're beautiful!" Although she generally enjoyed her term in Rome, she was disappointed to have the stereotype of lecherous Italian men proved true (Berlusconi does nothing to help that image, either...).
My most recent example of street harassment was a couple of days after my PhD viva. I was walking through Headingley in the morning and had to pass a group of (drunk already at 10 am?) rugby fans, and was told "You're gorgeous!" When I didn't respond and kept walking, he yelled "Bitch!" It was a bit of a wake-up call, actually--even after earning a PhD, to a drunk man in the street I was just another woman to harass.
Street harassment is a negative aspect of local culture in countries all over the world. Local women may become immune to it, after many years of ignoring it, but for an international student or tourist, unwanted attention can have long-term effects on their impressions of the host country.