Learn German: Wir sind gezwungen, hier auszuharren, obwohl alle außer mir Platzangst haben. - We are forced to hold out here, although everyone except me has claustrophobia.

The phrase gezwungen sein means to be forced or to be compelled, acting as a formal alternative to the modal verb müssen. Because it is not a true modal verb itself, it requires a secondary clause with zu plus an infinitive verb. This is why we see the structure gezwungen, hier auszuharren.

Why is it auszuharren as one word instead of zu ausharren?

The verb ausharren (to hold out or endure) is a separable verb. When a separable verb needs to be in its zu infinitive form, the zu is sandwiched between the separable prefix aus and the root verb harren, combining into the single word auszuharren.

Doesn't Platzangst literally mean fear of open squares? Why is it translated as claustrophobia?

You are right about the literal translation! Clinically, fear of open spaces is agoraphobia, and fear of confined spaces is Klaustrophobie. However, in everyday spoken German, people almost universally use the word Platzangst to mean claustrophobia (a fear of lacking space). It is a widespread colloquial habit that has become entirely standard.

Why does the sentence use mir instead of mich in the phrase außer mir?