Having strong ties to family and friends has long been identified as an important part of being happy and healthy. However, if forced to choose which is more important, American researchers now say friendship is more important than family.

【翻译】与家人和朋友有着密切的关系，长久以来被认为是幸福和健康的重要组成部分，然而，如果非要选择哪一个更重要，美国研究人员现在认为友谊比家庭更重要。

【结构分析】

第一句：Having strong ties to family and friends（主语：动名词充当；语义：与家人和朋友有着密切的关系）has long been identified （谓语：被动语态；语义：长久以来被认为）as an important part of being happy and healthy.（主语补足语：补充说明主语，由as...介词短语充当；语义：是幸福和健康的重要组成部分）

第二句：However, if forced to choose which is more important（省略式条件句）, American researchers now say friendship is more important than family.（主句）

1. 条件句：if (they are) forced to choose which is more important：

be forced to do被迫做某事/不得不做某事/非做某事不可

which is more important：choose的宾语从句

2. 主句：American researchers （主语）now say （谓语）friendship is more important than family.（宾语从句）