Restrooms/toilets

On average, most American public restrooms/bathrooms/lavatories are not as clean or pleasant as equivalent public toilets found in Western Europe or Japan. Some may be pristine, such as in upscale shopping malls, fine restaurants, or commercial office buildings. Others will be shockingly unkempt, such as at many gas stations and bars. Some toilet stalls offer disposable toilet seat covers if you are bothered by this, but those are far from being universal. (The main reason is that most American public facilities do not hire a janitor who is tasked specifically with maintaining the restrooms full-time; rather, American restrooms tend to be maintained by a facility's general janitorial staff only a few times a day, with predictable results.)

Basically all public buildings are required to have handicapped accessible restrooms. Increasingly, restrooms offer baby changing stations in both the men's and women's restroom (these are mostly seen in shopping places and restaurants); a few places have a separate "family" restroom which is single-occupancy but spacious.

For little children who need to be monitored or assisted, it's generally acceptable for them to use the restroom of the parent they're with (little girls can go with dad to the men's room, and vice versa). The other way around (dad going to the ladies' room) is usually not okay.

Dress.

Today, dress in the U.S. tends to be fairly casual. For everyday clothes, jeans and T-shirts are always acceptable, as are shorts when the weather is suitable. Sneakers (athletic shoes) are common; flip-flops and sandals are also popular in warm weather.

At the workplace, business casual (slacks, understated collared shirts without a tie, and non-athletic shoes) is now the default at many companies; more traditional industries (e.g. finance, legal, and insurance) still require suits and ties, while others (e.g. computer software) are even more casual, allowing jeans and even shorts.

When dressing up for nice restaurants or upscale entertainment, a pair of nice slacks, a collared shirt, and dress shoes will work almost everywhere. Ties for men are rarely necessary, but jackets are occasionally required for very upscale restaurants in big cities (such restaurants almost always will have courtesy jackets on offer if you forget).

At the beach or pool, men prefer loose bathing trunks or boardshorts, and women wear bikinis or one-piece swimsuits. Nude bathing is not generally acceptable and is usually illegal except at certain private beaches or resorts; even women going topless is not usually accepted by most people, and is also illegal in some states.

Generally, Americans accept religious attire such as hijab, yarmulke, and burqa without comment. However, do be aware that in places of heightened security such as banks, municipal buildings, and so on, wearing clothing which covers the face may be regarded as suspicious behavior and is generally unadvisable.