I know divorce is quite common in America, where it isn't that difficult to dissolve ones marital union. I have been married over 22 years, so I guess it's hard for me to understand why it can be so easy for some people.
Has divorce been around as long as the institution of marriage?
Divorce didn't become available for many years after marriage. Divorce laws vary around the world too. Most countries require a court to resolve many issues like child support, visitation, alimony, etc.
Is divorce prevalent in the United States?
Oh yes, with many reasons that one can divorce, such as infidelity, controlling spouse, financial issues, incompatibility, etc. 
What's the biggest issue that couples cite as causes for divorce?
Grounds for divorce (United States)
Grounds for divorce are regulations specifying the circumstances under which a person will be granted a divorce. Each state in the United States has its own set of grounds. A person must state the reason they want a divorce at a divorce trial and be able to prove that this reason is well-founded.
Several states require that the couple must live apart for several months before being granted a divorce. However, living apart is not accepted as grounds for a divorce in many states
get 'Declan' on the street, at restaurants, everywhere. Declan is me so to hand it over is difficult." He also felt humble that viewers thought the character would not be the same played by another actor, adding: "I'm very humbled that a lot of people think that – I can understand why fans would feel that way because I starred as Declan for the past three years and that's all anyone knows."
Mullally later stated he did not know he was auditioning for a recast