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?
Most cases are infidelity and financial issues. Of course, each state has different sets of rules on divorce, and some require that couples live apart for months before they will grant one.
Gosh I didn't know getting a divorce was so strict.
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The United States allows a person to end a marriage by filing for a divorce on the grounds of either fault or no fault. In the past, most states only granted divorces on fault grounds, but today all states have adopted a form of no fault divorce. Fault and no-fault divorces each require that specific grounds be met. A no fault divorce can be granted on grounds such as irretrievable breakdown of the marriage, irreconcilable differences, incompatibility, or after a period of separation, depending on the state
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