Using xsl:evaluate to evaluate value of XPath - xslt

Question

I am trying to use xsl:evaluate to get the value referecend by an XPath, but can't get it to work.
Here is an example (it would not make sense to use xsl:evaluate for this in a real application).
So what I expected in my code was to evaluate the XPath expression defined and store the value of that referecend attribute in a variable to be used in my code.
There must be something I don't understand in the way to use xsl:evaluate.
Input XML
<?xml version="1.0" encoding="UTF-8"?>
<Country name="USA">
<State name="California">
<City name="Los Angeles"/>
<City name="San Francisco"/>
</State>
</Country>
Expected output
<?xml version="1.0" encoding="UTF-8"?>
<Country name="USA">
<State name="California">
<City name="USA"/>
<City name="San Francisco"/>
</State>
</Country>
My XSLT code
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="#all"
version="3.0">
<xsl:output method="xml" indent="yes"/>
<xsl:template match="node() | #*">
<xsl:copy>
<xsl:apply-templates select="node() | #*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="#name[.='Los Angeles']">
<xsl:variable name="xPathString" select="'ancestor::Country/#name'"/>
<xsl:variable name="input" as="xs:string">
<xsl:evaluate xpath="$xPathString"/>
</xsl:variable>
<xsl:attribute name="name" select="$input"/>
</xsl:template>
</xsl:stylesheet>
Error message I am getting
Error at char 0 in expression in xsl:evaluate/#xpath on line 19 column 40 of Test.xsl:
XPDY0002 Dynamic error in expression {ancestor::Country/#name} called using xsl:evaluate.
Found while atomizing the value of variable $input
In template rule with match="#name[xs:string(.) eq "Los Angeles"]" on line 15 of Test.xsl
invoked by xsl:apply-templates at file:/C:/Users/ck3503/Documents/Repositories/outilscrea/specifications/profil/xslt/Test.xsl#11
In template rule with match="(comment()|(processing-instruction()|(element()|text())))" on line 9 of Test.xsl
invoked by xsl:apply-templates at file:/C:/Users/ck3503/Documents/Repositories/outilscrea/specifications/profil/xslt/Test.xsl#11
In template rule with match="(comment()|(processing-instruction()|(element()|text())))" on line 9 of Test.xsl
invoked by xsl:apply-templates at file:/C:/Users/ck3503/Documents/Repositories/outilscrea/specifications/profil/xslt/Test.xsl#11
In template rule with match="(comment()|(processing-instruction()|(element()|text())))" on line 9 of Test.xsl
invoked by built-in template rule (text-only)
Dynamic error in expression {ancestor::Country/#name} called using xsl:evaluate. Found while atomizing the value of variable $input

Answer 1

I think you want
<xsl:variable name="input" as="xs:string">
<xsl:evaluate xpath="$xPathString" context-item="."/>
</xsl:variable>